Prior to departure of a large passenger aircraft all aircraft doors are placed into a so-called “armed mode” by the cabin crew. If an evacuation is required and the doors are opened while armed, the opening of the door activates an evacuation slide pack, which expands out of a slide container. Once the slide is outside it will automatically inflate into its final useable position. Inadvertent slide deployment occurs when the operator of the aircraft door attempts to open the door in normal condition (no emergency) when it is in the armed mode. High follow-up-costs have become a burden for the airlines during the last years. Slides are inadvertently deployed both by trained cabin crew and by other persons like ground or maintenance staff.
This occurrence is not specifically limited to certain aircraft manufacturers and their door technologies. Common reasons for inadvertent slide deployment usually lie in time pressure or high workload for maintenance crew, ground crew and cabin crew, often occurring ad hoc situations and thus deviations from standard procedures in the aircraft, service in different aircraft types within shortest periods (mixed fleet flying).
Today indications exist that are activated when operating the door control handle while the slide is armed. Nevertheless inadvertent slide deployments occur. One reason for this is a short reaction time needed to stop the movement of the handle. A known invention for preventing inadvertent slide deployment in an aircraft is an alarm system comprising a sensor that is able to detect an operator gripping the handle of an aircraft door. If the handle detects that it is about to be gripped while the door is in armed mode an acoustic alarm signal is initiated. The acoustic signal in this case is realised as a recorded voice being played back, so that the operator hears a voice telling that the door is armed and that the slide will deploy. The operator then has to mentally realise that pulling the door handle will inadvertently lead to the deployment of the slide. The operator has to reconsider his intention, stop to pull the handle, and move his hand to disarm the slide.
This system is disadvantageous, because the alarm occurs only when the door handle is about to be gripped which may be too late for effectively preventing the inadvertent slide deployment. The time period needed for reconsidering the intention to pull the door handle may be too long so that the reason for the alarm signal is understood too late. Also, a trained operator—in case the operator belongs to the cabin crew—usually operates the door handle in a situation where a lot of passengers produce noise while removing their seat belts, opening overhead stowage bins, pulling out pieces of hand luggage, pulling on jackets, talking, switching on mobile phones that signalize initial reception with a beep etc. so that a rather late acoustic alarm will not properly be perceived and considered, so that the known system might not effectively prevent inadvertent slide deployment.
Further, an untrained operator does not automatically receive a proper and easy-to-realise information about the door and slide status and what has to be done in order to prevent the slide deployment. Especially for local maintenance staff and ground staff operating all over the world it might be challenging for them while opening the aircraft door in order to get out of the aircraft, receive food trolleys from a catering service, etc to understand a voice message in English or whatever language. In this case, due to misunderstanding of the voice message, it takes probably too much time to react accurately to the voice message and stop the action of opening. Even more it is probable that the person does not listen to the broadcasted language consequently the content of the message.
It is an object of the invention to provide a system for preventing inadvertent slide deployment in an aircraft that is able to effectively prevent door operation when the aircraft door is in an armed mode even if the door operator is in a stress situation, is untrained or is not capable to understand a spoken warning. A further object of the invention is to provide a system for preventing inadvertent slide deployment that is cost effective, easy to retrofit and able to be automatically switched on (on ground) or off (during flight) where an inadvertent door handle movement is per se not possible.